In the tissue manufacturing process, the paper sheet is dried by means of a steam heated drying cylinder, termed a Yankee. Adhesive materials are used to coat the Yankee surface in order to adhere the wet sheet to the dryer. This improves heat transfer, allowing more efficient drying of the sheet. Most importantly, these adhesives provide the required adhesion to give good creping of the dry sheet. Creping is the process of impacting the sheet into the metal blade, thus compressing the sheet in the machine direction, creating a folded sheet structure. Creping breaks a large number of fiber-to-fiber bonds in the sheet, imparting the qualities of bulk, stretch, absorbency, and softness which are characteristic of tissue. The amount of adhesion provided by the coating adhesive plays a significant role in the development of these tissue properties.
The Yankee coating also serves the purpose of protecting the Yankee and creping blade surfaces from excessive wear. In this role, the coating agents provide improved runability of the tissue machine. As creping blades wear, they must be replaced with new ones. The process of changing blades represents a significant source of tissue machine downtime, or lost production, as creped product cannot be produced when the blade is being changed. Release agents, typically hydrocarbon oils, are used in association with the coating polymers. These agents aid in the uniform release of the tissue web at the creping blades, and also lubricate and protect the blade from excessive wear.
Each tissue mill and even each tissue machine has different Yankee coating requirements. This is caused by differences in furnish, water chemistry, wet end chemical additives, machine conditions, dryness of the sheet to be creped, and degree of creping desired. Due to the differences in coating requirements needed from machine to machine, it is difficult for one coating polymer to perform in an optimal manner on each machine.
It has recently been discovered that a superior adhesive for Yankee Dryers, used to produce creped paper products, comprises glyoxated poly-acrylamide/diallyldimethyl ammonium chloride (DADMAC). The use of these resins as creping adhesives is disclosed in the application of Arthur James Begala and Gary S. Furman Jr. for Yankee Dryer Adhesives filed 5/18/90, Ser. No. 525806. The disclosure of this application is incorporated herein by reference. While these resins have provided superior Yankee Dryer adhesives, it would even be more beneficial to the art if they could be improved upon.